In recent years, liquid crystal display devices have been widely used as display devices of smartphones, personal digital assistants (PDAs), tablet computers, vehicle-navigation systems, etc. In general, a liquid crystal display device comprises a liquid crystal panel, and a backlight device overlaid on the rear surface of the liquid crystal panel and illuminating the liquid crystal panel. The backlight device includes a reflective layer, a light guide, an optical sheet, a light source unit which emits light incident on the light guide, a case (bezel) in which these members are accommodated, etc. The light source unit includes a wiring board and a plurality of light sources, for example, light-emitting diodes (LEDs) mounted on the wiring board.
As light source units, a side view type LED and top view type LED are known. In the side-view type LED, the light-emitting surface is provided normal to the mounting surface of the wiring board, whereas in the top-view type LED, the light-emitting surface is provided to face the mounting surface of the wiring board to be parallel thereto. In either type, normally, the LED comprises an LED chip which is the center of light emission, and a case (package) in which the LED chip is accommodated.
In recent years, in connection with the reduction in the thickness or size of backlight devices and liquid crystal display devices, the reduction in the size of each LED itself has been required. When the thickness or size of each LED is reduced, it is necessary to reduce the size of the package and the thickness of the walls of the package. However, when the thickness of the walls is reduced, light may leak out from the side surfaces other than the light-emitting surface. When light leaks out, the luminance near the light source unit may become nonuniform, thereby having a detrimental effect on the display quality.